The present disclosure relates to an internal combustion engine, for example for driving a vehicle. In particular, an internal combustion engine with Miller or Atkinson closing times is described.
Only a few years after the basic disclosures relating to the four-stroke principle by A. E. Beau de Rochas and N. A. Otto, closing times of the inlet valve that deviate greatly from bottom dead centre (BDC) were implemented in order that, as a result of a longer expansion stroke compared with compression, the combustion gas expands further, cools more greatly and thus the energy contained in the gas is exploited better. In particular, it has been known for a long time that, as a result of very early closing (before BDC) or very late closing (for example more than 40° after BDC) of the inlet valve according to R. Miller or according to J. Atkinson, high specific loads (i.e. the mechanical power output in relation to the fuel rate) with lower peak pressures (i.e. the maximum of the cylinder pressure in the cycle after top dead centre of firing) than in conventional control timing can be achieved. Provided that the supercharging system has good efficiency levels, it is also possible for the specific fuel consumption (i.e. the reciprocal of the specific load) to be lowered here. At the same time, lower nitrogen oxide emissions arise on account of lower process temperatures.
These advantages can be found especially in the range of high levels of power. In the range of average and lower levels of power, the drawbacks resulting from the lower volumetric efficiencies predominate, which are not yet compensated by efficient supercharging. Generally, Miller or Atkinson control timing is therefore applied in combination with a variable valve drive, which allows the control timing to be switched or changed between the power ranges. The document WO 2001/21939 A2 describes a hydraulic mechanism for operating a valve of an internal combustion engine, said hydraulic mechanism allowing a Miller cycle under partial load and allowing the Miller cycle to be deactivated under full load. The document DE 10 2007 022 145 A1 describes a switchable valve drive of an internal combustion engine with an axially displaceable cam on the camshaft.
However, such switchable valve drives are associated with complicated control mechanics, which increase the production costs of the internal combustion engine, increase the installation space therefor and/or reduce the reliability of the internal combustion engine.